This application claims the benefit of the application Ser. No. 0003488 filed Mar. 17, 2000 in France, which is incorporated herein by reference.
This invention relates to a motor operator, and, more particularly, to a motor operator for circuit breakers.
The use of motor operators to allow the motor-assisted operation of electrical circuit breakers is well known. A motor operator is typically secured to the top of a circuit breaker housing. A lever within the motor operator mechanically interacts with a circuit breaker operating handle, which extends from the circuit breaker housing. The lever is operatively connected to a motor within the motor operator. The motor drives the lever, which, in turn, moves the operating handle to operate the circuit breaker. The operating handle is moved between xe2x80x9conxe2x80x9d, xe2x80x9coffxe2x80x9d, and xe2x80x9cresetxe2x80x9d positions, depending on the rotational direction of the motor.
A plurality of buttons external to the motor operator controls electrical current to the motor. The rotational direction of the motor is changed depending on which of these buttons is selected by operating personnel. Thus, the operating personnel can select one button to place the operating handle in the xe2x80x9conxe2x80x9d position, and another button to place the operating handle in the xe2x80x9coffxe2x80x9d or xe2x80x9cresetxe2x80x9d positions.
When the handle is moved to the xe2x80x9conxe2x80x9d position, electrical contacts within the circuit breaker are brought into contact with each other, allowing electrical current to flow through the circuit breaker. When the handle is moved to the xe2x80x9coffxe2x80x9d position, the electrical contacts are separated, stopping the flow of electrical current through the circuit breaker. When the handle is moved to the xe2x80x9cresetxe2x80x9d position, an operating mechanism within the circuit breaker is reset, as is necessary after the operating mechanism has tripped in response to an overcurrent condition in the electrical circuit being protected by the circuit breaker.
Typically, the motor used within such motor operators is a series motor, as shown in FIG. 1. Series motors are so called because the field coils of the motor are electrically in series with the rotor coil. FIG. 2 is a diagram of the stator of a series motor. The field coils are wound around magnetic pole pieces, called shoes. The field coils and shoes produce the main magnetic field. When current passes through the field coils, one shoe becomes a north pole while the other becomes a south pole. Electrical connection between the field windings and the rotor windings (not shown) is made by brushes (not shown) in contact with a commutator (not shown) of the rotor, as is known in the art.
In order to change the rotational direction of a series motor, the direction of the current flow to either the rotor or the field must be reversed. A typical arrangement for reversing the current flow is shown in the circuit diagram of FIG. 3. In this arrangement, two double-throw type switches are arranged to operate the motor in two directions, one to position the breaker in the xe2x80x9conxe2x80x9d position, the other to position the breaker in the xe2x80x9coffxe2x80x9d and xe2x80x9cresetxe2x80x9d positions. As can be seen in FIG. 3, this arrangement requires five electrical connections to be established at the motor operator. It would be desirable to reduce the number of electrical connections in order to reduce the amount of time needed to install and remove the motor operator.
In an exemplary embodiment of the invention, a motor operator for a circuit breaker has a series motor, which includes a first external terminal coupled to a first half inductor and a second external terminal coupled to a second half inductor. A third external terminal is coupled to a rotor. The first external terminal and the third external terminal form a first electric path, and the second external terminal and the third external terminal form a second electric path.